Traditional toilet disposes the tank on the seat body. Due to the water gravity, water in the tank easily enters the flushing ring passage of the toilet to flush the bowl. But this kind of toilet occupies large space, and it is not convenient for package and transportation and it costs high. Therefore, there is a kind of toilet with low tank; the tank is disposed at the interior portion of the rear side of the seat body that it reduces much occupying space. However, this low tank type toilet has disadvantages: the height difference between the water level in the tank and the lip portion of the toilet (the flushing ring portion) is small, even the water level in the tank is lower than the lip portion, resulting in that when water flushes, the tank can provide enough water to satisfy the bowl flushing need.
A patent application is disclosed in the Chinese patent database with publishing number CN103104014A and title a lip portion water supply converting device of a low tank type toilet, in which the flushing water from the inlet valve is guided to the lip portion of the toilet to flush the bowl of the toilet by components like clean water supply pipe (110), supply water converting component (130), water level adjusting component (150), float ball (160), floater (240), pipes (220), etc. However, this low tank toilet still has disadvantages: the pipe body (220) is connected to the inlet valve and the tank, so water level of the clean water flushing pipe (110) and the water level of the tank directly influence the water level in the pipe (220), the inlet water from the inlet valve provides pump force to the water in the pipe (220), water in the pipe (220) is directly pumped to the toilet. That is to say, when in work state, the water level in the pipe is influenced only a bit by the water level in the tank but a lot by inlet pressure and the pump force of the inlet valve. The floater (240) in the pipe (220) senses the water level in the pipe but not the water level in the tank to float up and down. Therefore, the inlet pressure of the inlet valve and the pump performance directly influence the water level in the pipe, and influencing the switch of the water supply switch component. Namely the water supply switch device provides different supply water converting volumes in different working pressure with the same set of inlet valve and discharging valve. During flushing the ring passage, it may lead to bad flushing effect when the water supply volume is not enough or waste water when the water supply volume is abundant. In addition, this solution has disadvantages of many components and complicated structure.